1. Field of the Technology
The present disclosure relates to cutting tools and cutting inserts for machining metallic materials.
2. Description of the Background of the Technology
As used herein, the term “metal cutting” broadly refers to machining, turning, milling, drilling, boring, planing, shaping, reaming, and like material removal operations performed on metallic (i.e., metal and metal alloy) materials. Cutting tools used in metal cutting typically are subjected to high loads and high temperatures. During metal cutting, the cutting tool applies a high load to the metallic workpiece to deform the workpiece. Because of the relative motion of the workpiece and the cutting edge of the cutting tool, shear deformation is produced in the metallic workpiece, generating metal chips from the workpiece. A cutting tool tip or cutting insert will generally include a rake face, which is a portion of the tip or insert that encounters and further deforms chips after the chips are formed at the cutting edge of the tip or insert. Cutting inserts may also include additional features that control chip size and shape. The chips produced in metal cutting are hot from deformation and frictional forces and are in close contact for a time with the cutting tip or cutting insert.
Because cutting inserts experience high loads and frictional contact with the workpiece and the machined chips, the cutting insert, and particularly the insert's cutting edge, is heated to very high temperatures. For example, cemented carbide cutting inserts may be heated to temperatures greater than 1,800° F. (982° C.) during cutting of hard steels. High cutting insert temperatures increase wear during metal cutting and, thus, reduce cutting insert service life. Machine tool operators can reduce tool speed to at least partially counteract high temperature-induced cutting insert wear. Reducing tool speed, however, may adversely affect the finish quality of machined surfaces produced on a metallic workpiece. Instead, a coolant is typically used to cool the cutting edge of a cutting insert during metal cutting.
Metal cutting coolants, which are also referred to as cutting fluids, serve to lubricate the workpiece and reduce frictional forces at low cutting speeds. At higher cutting speeds, coolants predominantly act to cool the workpiece and the cutting insert, and assist in flushing chips away from the cutting insert. The use of coolants in metal cutting significantly increases cutting insert service life, reduces unintended deformation of the workpiece, improves surface finish quality, and enhances chip removal and handling.
Traditionally, coolants are fed from an external source to the region of the interface between the cutting edge of a cutting insert and the workpiece. For example, a flow of coolant may be flooded onto both the workpiece and cutting insert through tubing from an external coolant source. Another method of applying coolant to the cutting edge/workpiece interface region is to direct a jet of coolant at the interface region. Still another method of applying coolant involves misting a coolant with an air jet and directing the mist at the cutting edge/workpiece interface region.
Conventional methods of applying coolants to a cutting edge/workpiece interface region are inefficient. For example, an excess amount of expensive coolant typically is applied during metal cutting to better ensure that coolant will contact the interface region and remove heat from the cutting insert's cutting edge. However, although excess coolant is applied, because of the tight tolerances at the interface region and the continuous generation of chips at the interface, less than an optimal amount of coolant is delivered to the interface region to efficiently and effectively reduce the temperature of the cutting insert's cutting edge. As such, the operating temperature of the cutting insert's cutting edge may remain very high, reducing cutting insert service life.
Accordingly, a need exists for an improved arrangement for reducing the temperature of the cutting edge of a metal cutting insert during cutting operations. In particular, a need exists for an improved system to deliver coolant to the cutting edge/workpiece interface during cutting operations.